Prolongation of sieve capacity by controlled desulfurization



May 11, 1965 A. A. YEo ETAL 3,183,182

PROLONGATION OF SIEVE CAPACITY BY CONTROLLED DESULFURIZATION Filed Aug.13, 1962 2 Sheets-Sheet 1 FIGJ.

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May 11, 1965 PROLONGATION 0F SIEVE CAPACITY BY CONTROLLEDDESULFURIZATION Filed Aug. 15, 1962 A. YEO ETAL 2 Sheets-Sheet 2 A/ :9.YE'O CL/ VE' .//CKS' 'P0652 7.' L. MOWLL United States Patent O 3 183182 PROLONGATIGN F SiIEVE CAPACHTY BY CONTROLLED DESULFURIZATION AlanArthur Yeo, Clive Leonard Hicks, and Roger Tem- 3,l83,l82 Patented May11,Y 1965 ice The catalyst may be any one or more of the knownsulfur-resistant metals or metal compounds having hydrogenating activityselecting from Groups Vla and VIII of the Periodic Table, preferablysupported on a refractory pieton Lewis Mowil. Sunburymmhames, Middlesex,5 oxide, for example alumina. Particularly suitable cata- England,assignors to The British Petroleum Company lysts are those having cobaltand molybdenum oxides on Limited, of Britannie House, London, England, aBritish a refractory oxide support, for example alumina,preferl'UiIl-Stoek COlPlafGll p ably containing l-l0% weight cobaltoxide expressed as Filed Aug- 13, 1962i ser N9 @16,476 CoO and 4-40%weight molybdenum oxide expressed Claims priority, application GreatBritain, Sept. 8, 1961, lo as M003.

9 Cla mgzszl/ g%)8 212) The molecular sieveV separation may comprise anabsorption stage and a desorption stage with an intervening This caserelates to separation processes using molecupurge stage. Suitableconditions may be selected from lar sieves for the separation ofstraight-chain hydrocarthe following ranges:

Temperature Pressure Space Velocity Period Absorption G-600 C., pref.0-500 p.s.i.g.,.pref. 0.1-3.0 v. v./11r., 10 sec. to 20 min.,

30D-450 C. 10G-300 p.s.i.g. pref. 0.5-2.0 pref. 1 to 10 min. Purge20D-600 C., pref. 0-500 p.s.i.g., prei. SGYt/)gn/GMISV, 10 sec. to 20min.,

3004150a C. 10o-300 psig. ipo-300 pref. 1 t0 10 min. Desorption 200000o.,pref. 0-500 p.s.i.g.,pref. 0.1-4.0 v.]v./hr., 0.5m 50 min., pref.

30o-450 C. 10o-400 psig. pref. 0.5-2.0 5 to 20 min.

v./v./hr;

bons from -mixtures of the same with branched-chain The molecular ksieveseparation is preferably carried and/ or cyclic hydrocarbons. out in thevapour phase and may be isothermal and/or Certain natural and syntheticzeolites are well known isobaric. The preferred purging agent isnitrogen and to possess the property of preferentially absorbing certhepreferred desorbing agent are straight-chainparaiiins tain types ofhydrocarbons. These zeolites, known as for example n-butane andn-pentane. molecular sieves, have crystalline structures containing aThe process is suitable for treating any feedstock conlarge number ofpores of uniform size. In different zeotaining straight-chainhydrocarbons and branched chain lites these pores may vary from about 4A. to l5 A. in and/ or cyclic hydrocarbons together with sulfur in andiameter but in any one zeolite the pores will be of subamount greaterthan 0.011% weight. The process is pairstantially uniform size. Azeolite having pore diameter ticularly suitable for the treatment ofpetroleum feedof about 5 A. is suitable for the separation of straight-35 Stocks containing more than 1% weight sulfur. Examchain hydrocarbonsfrom mixtures of the same with ples of suitable feedstocks includepetroleum fractions branched-chain and/or cyclic hydrocarbons.boiling'within the range 85 to 400 C. and the process It is also knownthat molecular sieves are sensitive to is particularly suitable fortreating gas oils, i.e., fractions polar compounds, including sulfurcompounds, and that boiling between 20G-400 C. these compounds have theeffect of deactivating a sieve, 40 Y It has been found that by limitingthe extent of desuli.e., reducing its absorptive capacity. It has,therefore, furization to between 0.002 and 0.015% a longer sieve beenaccepted that it is desirable to eliminate these polar life, ie, a OHgefPefed before regeneration beCOmeS IleC- materials as far as possiblefrom feedstocks to molecular essary, is obtained than would be obtainedby hydrocatasieve separation processes, for example in the case oflytically desulfurizing to alevel of 0.001% weight. While sulfurcompounds by desulfurization. the reason for this is not clear it issuggested that the It has now been found, however, that there is aposisevere conditions necessary to desulfurize to a level below tiveadvantage in desulfurizing a hydrocarbon feedstock @002% Weight mayPIOUCe materials, fOr example P013" to a molecular sieve separationprocess to an intermediate nuclear MOIHHCS 0r OleIlS, Whieh adverselyaffect the level only and according t0 the present invention a proc.activity of the sieve to an extent which outweighs the ess forseparating straight-chain hydrocarbons from feedadvantage COUferfed bythe eXtra deSUlflfZatOlstocks containing the same in admixture withbranched- The invention is illustrated by the following comparachainand/or cyclic hydrocarbons by extraction with a tive eXamP1e 5 A.molecular sieve comprises first subjecting the feed- EXAMPLE lstock to adesulfurization step wherein the sulfur content Two samples of astraight-run Middle East gas oil 1s reduced to a value within the range00in-0.015% 55 honing between 220 and 345 C. and containing 1.14%weight. weight sulfur were hydroned under the conditions indi- Thepresent invention applies particularly to processes cated in Table lbelow, the sulphur contents being reduced in which the sulfur content ofthe feedstock is reduced to 0.01% weight and 0.001% weight respectively.by hydrocatalytic desulfurization. The conditions neces- Table 1 sary toreduce the sulfur content to the required level by hydrocatalyticdesulfurization may readily be determined Feed to Process A B byexperiment and may be selected from'the following Ial'lgeSZ HydroflningData: Y Y n Temperature 3004180 Cs preferably Catalyst {ili/tjji iii'fi370n430 C, 65v *o Aluminabaiance-- 9A11imiis`,pa1s'nce. Pressure s.502000 psig., preferably grespurtlifsgjjjj 400 fo,

500. p s i.g Feed Rate, v./v./hr 3.3, Space Velocity 0.5-20 v./v./hr.,preferably pmtfgg Rate Sc'ffb' 1000 1 1() v /VJhL Sulfur Content;(Total), 0,001 Hydrogen rate (recycle or 50l0,000 s.c.f./b., prefer- 70Percent Wt' once-through) ably 500-4000 s.c.f./b.

1 Present as oxides,

The desulfurized samples were then subjected to molecular sieveextraction using a Davison Co. A. type sieve under the conditionsindicated in Table 2 below:

The purging agent was nitrogen and the desorbing agent was n-pentane.

The production rate of the process was plotted against elapsed time foreach sample and the results are plotted in the accompanying FIG. 1.

In FIG. 1 the Utilized sieve capacity per cycle is the weight ofn-parains produced per cycle per 100 grams of sieve. It is seen that thedecay rate of the sieve is less when treating the gas oil of high sulfurcontent.

In FIG. 2 the eiect of sulfur on sieve life is shown at levels of 1.14%,0.57% and 0.01% weight. In this case the molecular sieve extraction wasisothermal and isobaric at '380 C. and atmospheric pressure. It is seenthat at the higher sulfur levels of 1.14% and 0.57% the decay rate israpid as would be expected in view of the prior art.

We claim:

l. A process for separating straight-chain hydrocarbons from feedstoclrsof petroleum fractions boiling between 85400 C. containing thestraight-chain hydrocarbons in admixture with branched-chain and/orcyclic hydrocarbons by extraction with a 5 A. molecular sieve whereinthe feedstock containing more than 1% weight sulfur hydrocatalytc is rstsubjected to a desulfurization step in which the sulfur content isreduced to a value within the range 0.002 to 0.015% weight byhydrocatalytic desulfurization in the presence of a catalyst cornprisingat least one metal selected from Groups VIa and VIII of the PeriodicTable supported on a refractory oxide, at a temperature between 30G-480C., a pressure between -2000 p.s.i.g., a space velocity between 0.5-20v./v./hr. and a hydrogen ilow rate between 50-10,000 s.c.f./ b.

2. A process as claimed in claim 1 wherein the feed- `stock boilsbetween 200-400" C.

3. A process as claimed in claim 1 wherein the hydrocatalyticdesulfurization is carried out at a temperature between 370-430 C., anda pressure between SOO-1500 p.s.1.g.

4. A process as claimed in claim 3 wherein the hydrocatalyticdesulfurization is carried out at a space velocity between 1-.10v./v./hr., and hydrogen llow rate between 50G-4,000 s.c.f./'b.

5. A process as claimed in claim 1 wherein the molecular sieveextraction comprises a three-stage operation including an absorptionstage, a purge stage and a desorption stage.

6. A process as claimed in claim 5 wherein all three stages of themolecular sieve extraction are operated in the vapour phase.

7. A process as claimed in claim 6 wherein the molecular sieveextraction is operated isothermally and isobarically at a temperaturebetween ZOO-600 C. and a pressure between 0-500 p.s.i.g.

8. A process as claimed in claim 5 wherein the purging agent employed isnitrogen and the desorbing agent employed is selected from the groupconsisting of n-butane and n-pentane.

9. A process as claimed in claim 7 wherein the molecular sieveextraction is operated at a temperature between 200-600" C. and apressure between 0-500 p.s.i.g.

References Cited by the Examiner UNITED STATES PATENTS 2,859,256 11/58Hess et al 260-676 2,920,037 l/ Haensel 260-676 2,924,630 2/ 60 Fleck etal. 260-676 3,030,431 4/62 Manox et a1. 26o-6% 3,102,853 `9/63 Skarstromet al. 208-310 XR ALPHONSO D. SULLIVAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION May 11, 1965Patent No. 3,183,182

Alan Arthur Yeo et a1.

It is hereby certified that error appears in the above numbered patentreqiring correction and that the said Letters Patent should read ascorreoted,below.

Column 3, line 36, strike out "hydrocatalytic" and insert the same after"to a", same line 36, same Column 3.

Signed and sealed this 21st day of September 1965.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER AtlcstingOfficer

1. A PROCESS FOR SEPARATING STRAIGHT-CHAIN HYDROCARBONS FROM FEEDSTOCKSOF PETROLEUM FRACTIONS BOILING BETWEEN 85-400*C. CONTAINING THESTRAIGHT-CHAIN HYDROCARBONS IN ADMIXTURE WITH BRANCHED-CHAIN AND/ORCYCLIC HYDROCARBONS BY EXTRACTION WITH A 5 A. MOLECULAR SIEVE WHEREINTHE FEEDSTOCK CONTAINING MORE THAN 1% WEIGHT SULFUR HYDROCATALYTIC ISFIRST SUBJECTED TO A DESULFURIZATION STEP IN WHICH THE SULFUR CONTENT ISREDUCED TO A VALUE WITHIN THE RANGE 0.002 TO 0.015% WEIGHT BYHYDROCATATION STEP IN WHICH THE SULFUR CONTENT IS REDUCED TO A VALUEWITHIN THE RANGE OF 0.002 TO 0.015% WEIGHT BY HYDROCATALYTICDESULFURIZATION IN THE PRESENCE OF A CATALYST COMPRESING AT LEAST ONEMETAL SELECTED FROM GROUPS VIA AND VIII OF THE PERIODIC TABLE SUPPORTEDON A REFRACTORY OXIDE, AT A TEMPERATURE BETWEEN 300-480*C., A PRESSUREBETWEEN 50-2000 P.S.I.G., A SPACE VELOCITY BETWEEN 0.5-20 V./V./HR. ANDA HYDROGEN FLOW RATE BETWEEN 50-10,000 S.C.F./B.